The present invention relates to a method and a unit for the incineration or the thermal destruction of fluid wastes, in particular pollutant industrial wastes, be they in a liquid or gaseous state, by means of which it is possible at the same time to regenerate heat for technological uses or for other applications.
As is known, many industrial processes give rise to the formation of liquid or gaseous effluent or waste which, if not appropriately treated or disposed, would involve serious hazards for the environment as well as for man. The elimination of toxic or harmful wastes is especially critical since their recycling, or their elimination in a controlled dump, is often found to be impossible or inadvisable.
For these and other reasons various physical, chemical or biological treatment systems have been developed for the elimination of wastes, which have led to various plant engineering and process solutions.
The choice of the type of disposal plant and process generally depends on the type of waste, in addition to considerations of an economic and environmental nature.
Systems for the thermal destruction of wastes have also been developed which enable wastes to be decontaminated by means of high level thermal energy, such as to cause the breakdown of complex molecular bonds thus enabling total oxidation and simpler molecules, or substances which are harmless to man and which do not damage the environment, to be obtained.
For these reasons various systems for the thermal destruction of fluid wastes have been proposed whereby the wastes in the gaseous or pulverized state are fed into an incineration plant where they are heated to a high temperature level and maintained at this temperature for a residence or stay time sufficient to cause its total destruction.
More particularly plants with a single combustion chamber have been developed, in which the waste in a gaseous or pulverized state is injected and treated with the flame of a burner which rapidly raises its temperature bringing it to a required value. In general the use of a single combustion chamber does not ensure adequate remixing of the combustion gases with the gaseous or liquid pulverized waste nor total destruction of the same, so that there is serious risk of emission of unburnt or incompletely destroyed parts which may be trapped by the combustion fumes and emitted with them, polluting the environment.
Moreover, incomplete combustion of wastes or combustion thereof at insufficiently high temperatures or an insufficient stay time at this temperature may in any case involve the risk of emission of toxic or harmful substances, such as dioxine and furanes, a risk which must in all cases be eliminated or reduced to totally insignificant levels, below a strictest threshold.
Thermal destruction plants have also been developed with several combustion chambers formed by several sections connected in series, comprising a primary combustion chamber where the waste is blaze with the flame of a burner to bring it to a first temperature level, followed by a postcombustion chamber in which, by means of a secondary burner, the fumes from the primary combustion chamber are further heated to a second temperature level, equal to or higher than the temperature of thermal destruction. The postcombustion section is in turn connected to a stay chamber where the gases remain for a predetermined time at the temperature of thermal destruction before being sent to the stack, directly or through a heat regeneration system.
A similar plant is therefore developed on the level, the various sections being connected one to the other in series, in this way forming a several operative unit system with considerable overall dimensions, difficult to control and with lengthy running times. Moreover, from the point of view of thermal efficiency and waste destruction efficiency, these plants are not always found to be adequate or useable.
An object of the present invention is to provide a method and an unit for the thermal destruction of fluid wastes, designed to achieve high thermal and waste destroying efficiency, given that the combustion gases are maintained in a highly turbulence condition not only in the whole, but also in particular points of their path. In this way the emission of unburnt parts and/or hazardous substances due to incomplete destruction is avoided.
A further object of the present invention is to provide a method for the thermal destruction of pollant industrial waste effuents which requires small volumes of air and which enables high temperatures to be reached using a monolithically structured destroyer unit having small overall dimensions and relatively small volume.
A further object of the present invention is to provide a method and apparatus for the thermal destruction of industrial waste effluents, as explained previously, which enable operations under pressurized conditions, and therefore easy to operate and to control.
Yet a further object of the invention is to provide apparatus for the thermal destruction of industrial waste effluents in which the reaction takes place in substantially adiabatic conditions, along a path which develops substantially in a vertical direction.
A further object of the present invention is to provide apparatus as defined above which has a monobloc structure integrated with a heat regeneration section for the combustion gases, before the latter are sent to a stack, so as to reduce drops in pressure as far as possible, also making the heat regenerator and the entire apparatus easily accessible for their maintenance.
Yet a further object of the present invention is to provide a method and apparatus for the thermal destruction of waste effluents, as defined, which allow the pollutants emitted with the combustion fumes to be controlled accurately, maintaining them substantially below established legal levels.